Analysis of combined treatment of embolic stroke in rat with r-tPA and a GPIIb/IIIa inhibitor.

Suppression of platelet activation improves the efficacy of thrombolytic therapy for stroke. Thus, combination treatment with recombinant tissue plasminogen activator (r-tPA) and 7E3 F(ab')2, a GPIIb/IIIa inhibitor that binds the platelet to fibrin, may improve the efficacy of thrombolytic therapy in embolic stroke. Magnetic resonance imaging (MRI) was used to monitor treatment response in rats subjected to embolic middle cerebral artery (MCA) occlusion (MCAo). Animals were randomized into treated (n=12) and control (n=10) groups and received intravenous combination therapy or saline, respectively, 4 hours after MCAo. Magnetic resonance imaging (MRI) measurements performed 1 hour after MCAo showed no difference between groups. However, an increased incidence (50%) of MCA recanalization was found in the treated group at 24 hours compared with 20% in the control group. The area of low cerebral blood flow at 24 and 48 hours was significantly smaller in the combination treatment group, and the lesion size, as indicated from the T2 and T1 maps, differed significantly between groups. Fluorescence microscopy measurements of cerebral microvessels perfused with fluorescein isothiocyanate-dextran and measurements of infarct volume revealed that the combination treatment significantly increased microvascular patency and reduced infarct volume, respectively, compared with the control rats. The efficacy of combination treatment 4 hours after ischemia is reflected by MRI indices of tissue perfusion, MCA recanalization, and reduction of lesion volume. The treatment also reduced secondary microvascular perfusion deficits.

Mechanisms of blood-brain barrier breakdown after microembolization of the cat's brain.

Unilateral microembolization of the cat brain with carbonized microspheres 15 microns in diameter ten minutes (min) before death induced multifocal disruption of the blood-brain barrier (BBB) to horseradish peroxidase (HRP) in nine adult cats. The gross pattern of HRP extravasates was studied: (a) after five min of in vivo circulation, (b) following infusion of HRP immediately before chemical fixation, and (c) following infusion of HRP after 60 min of aldehyde fixation. Examination of the material from the three different experimental groups revealed no qualitative differences at the light microscopic level; specific features such as ring-shaped extravasations of HRP occurred irrespective of the mode of tracer injection. Tracer-filled pinocytotic vesicles and tubular profiles were abundant in the vascular endothelium after in vivo circulation of HRP, but were virtually absent after supravital and postmortem HRP administration. The results suggest that BBB breakdown for proteins after microembolization is not an energy-dependent process mediated by either pinocytosis or tubular-endothelial channel formation.

Middle cerebral artery thrombosis: acute blood-brain barrier consequences.

The effect of middle cerebral artery (MCA) thrombosis on the integrity of the blood-brain barrier (BBB) was studied in rats using horseradish peroxidase (HRP). Endothelial injury with subsequent platelet thrombosis was produced by means of a rose bengal-sensitized photochemical reaction, facilitated by irradiating the right proximal MCA segment with the focused beam of an argon laser. At 15 minutes following thrombosis formation, diffuse leakage of HRP was observed bilaterally within cortical and subcortical brain areas. Peroxidase extravasation was most dense within the territory of the occluded artery including neocortical areas and dorso-lateral striatum. Contralaterally, a similar distribution was observed but with less intense HRP leakage. Ultrastructural studies demonstrated an increase in permeability to HRP within arterioles, venules and capillaries. At these sites, the vascular endothelium contained HRP-filled pinocytotic vesicles and tubular profiles. Although less intense, bilateral HRP leakage was also observed following MCA stenosis or femoral artery occlusion. Endothelial-platelet interactions at the site of vascular injury may be responsible for releasing substances or neurohumoral factors which contribute to the acute opening of the BBB.

Pharmacological treatment following experimental cerebral infarction: implications for understanding psychological symptoms of human stroke.

Middle cerebral artery ligation in the rat produces decreases in catecholamine concentrations at brain sites uninjured by ischemic damage and a transient increase in spontaneous horizontal activity. Development of this hyperactivity can be blocked by postoperative treatment with the antidepressant, desmethylimipramine, or by preoperative destruction of norepinephrine terminals with 6-hydroxydopamine. These results suggest that ischemic damage to the cerebral cortex which injures some axonal branches of elaborately arborizing catecholamine-containing neurons may alter the biochemical and functional state of the entire system in its intact collateral axons. Thus the concept of stroke as a local injury producing symptoms by local structure-function relationships is conceptually inadequate, and poststroke symptoms must be evaluated with these "whole brain" concepts in mind. We suggest that the poststroke symptoms of apathy and depression may represent emotional changes which result from pathophysiological processes in catecholamine neurons far from the site of the stroke.

A rat model of reproducible cerebral infarction using thrombotic blood clot emboli.

The purpose of this study was the development of a model of embolic stroke with high reproducibility concerning infarct volume. In 37 male Sprague-Dawley rats, the internal carotid artery was embolized with in vitro preformed suspensions of autologous microemboli resembling arterial thrombi. With a method of continuous flow through the carotid arterial catheter, reflux of blood with uncontrolled clotting and embolization was avoided, thereby providing control animals free of ischemic damage. The embolized animals had arterial occlusions on angiograms immediately after embolization and no spontaneous recanalization on angiograms 2 h later. The cerebral blood flow measured by the intra-arterial 133Xe injection method decreased to 21-37% of baseline values. All embolized animals developed hemiparesis with spontaneous circling behavior, embolization with more than 150 microliters clot suspension resulted in hemispherical infarcts. There was a strong statistically significant correlation between amount of emboli, rate of vascular occlusion, and volume of infarcted tissue. This is the first model presented utilizing autologous in vitro microemboli imitating "white" arterial thrombi. The animals developed infarction, resembling human stroke.

Reperfusion after thrombolytic therapy of embolic stroke in the rat: magnetic resonance and biochemical imaging.

The effect of thrombolytic therapy was studied in rats submitted to thromboembolic stroke by intracarotid injection of autologous blood clots. Thrombolysis was initiated after 15 minutes with an intracarotid infusion of recombinant tissue-type activator (10 mg/kg body weight). Reperfusion was monitored for 3 hours using serial perfusion- and diffusion magnetic resonance imaging, and the outcome of treatment was quantified by pictorial measurements of ATP, tissue pH, and blood flow. In untreated animals, clot embolism resulted in an immediate decrease in blood flow and a sharp decrease in the apparent diffusion coefficient (ADC) that persisted throughout the observation period. Thrombolysis successfully recanalized the embolized middle cerebral artery origin and led to gradual improvement of blood flow and a slowly progressing reversal of ADC changes in the periphery of the ischemic territory, but only to transient and partial improvement in the center. Three hours after initiation of thrombolysis, the tissue volume with ADC values less than 80% of control was 39 +/- 22% as compared to 61 +/- 20% of ipsilateral hemisphere in untreated animals (means +/- SD, P = .03) and the volume of ATP-depleted brain tissue was 25 +/- 31% as compared to 46 +/- 29% in untreated animals. Recovery of ischemic brain injury after thromboembolism is incomplete even when therapy is started as early as 15 minutes after clot embolism. Possible explanations for our findings include downstream displacement of clot material, microembolism of the vascular periphery, and events associated with reperfusion injury.

Cerebral microembolization. I. Pathophysiological studies.

Unilateral embolization of the brain was performed in cats by intracarotid injection of 10.5 million carbonized microspheres (15 +/- 5 mu). Intracranial pressure increased from 6.1 +/- 1.5 to 14 +/- 2.3 mm Hg within two minutes and continued to rise more slowly to 24 +/- 18.3 mm Hg within four hours. Embolization caused a nonhomogenous distribution of microflow, but initially had no effect on global cerebral blood flow, nor on cortical oxygen tension. Yet, a functional suppression of cortical electrical and metabolic activity occurred. The ipsilateral EEG flattened irreversibly after 15 seconds; the contralateral EEG was transiently suppressed shortly thereafter. Arteriovenous difference of oxygen fell from 10.5 +/- 0.7 to 5.3 +/- 0.6 vol%, and the arteriovenous difference of glucose fell from 11.7 +/- 3.9 to 2.6 +/- 2.1 mg/100 ml as a consequence of reduced oxygen and glucose extraction. Subsequently, severe vasogenic brain edema, secondary ischemia, and severe functional suppression developed between two and four hours.

The effect of size, histologic elements, and water content on the visualization of cerebral infarcts.

We correlated the radiologic and pathologic examination of 13 human brains, analyzing the size, different histologic elements, and water content in 40 ischemic and hemorrhagic infarcts. Acute infarcts appear in the computerized cranial tomographic (CT) image as low density areas due to high content of fluid, however, a histological-chemical correlation is not concomitant. The addition of blood in hemorrhagic infarcts may result in a normal CT image. Subacute infarcts appear as low density areas, with lower attenuation values due to the presence of large amounts of lipids. Subacute lesions with prominent mineral deposits may be negative on CT scan. Chronic infarcts also appear as low density areas due to cavitation and residual fats. Attenuation values are slightly higher than those of subacute infarcts, possibly due to gliosis. Infarcts smaller than 2 cm in diameter are usually not visualized.

Reduction of coagulation factor XIII concentration in patients with myocardial infarction, cerebral infarction, and other thromboembolic disorders.

Coagulation factor XIII and plasma fibrinogen chromatographic assays have been performed serially in patients suffering from acute myocardial and cerebral infarction, and in others with disseminated intravascular coagulation. The findings were compared with 2 groups of "controls"; normal clinically-well subjects and hospitalized patients with cerebral infarction who exhibited minimal, stable, or improving neurological deficits. Substantial depression of factor XIII concentrations developed in the 3 patient groups, together with concomitant significant increases in the proportion and concentration of plasma high molecular weight fibrin(ogen) complexes (HMWFC). An inverse correlation (p less than 0.05) between coagulation factor XIII concentration and percentage of HMWFC was demonstrated in the early stages of the illness. These findings suggest that depression of coagulation factor XIII concentration in these states, is secondary to extravascular or intravascular coagulation and may reflect its degree.

Effects of NO-donors on thrombus formation and microcirculation in cerebral vessels of the rat.

Sodium nitroprusside (SNP) and 3-morpholinosydnonimine (SIN-1), are known to liberate nitric oxide (NO). In this study the effects of SNP and SIN-1 on thrombus formation in rat cerebral arterioles and venules in vivo were assessed using a helium-neon (He-Ne) laser. SNP infused at doses from 10 micrograms/kg/h significantly inhibited thrombus formation in a dose dependent manner. This inhibition of thrombus formation was suppressed by methylene blue. SIN-1 at a dose of 100 micrograms/kg/h also demonstrated a significant antithrombotic effect. Moreover, treatment with SNP increased vessel diameter in a dose dependent manner and enhanced the mean red cell velocity measured with a fiber-optic laser-Doppler anemometer microscope (FLDAM). Blood flow, calculated from the mean red cell velocity and vessel diameters was increased significantly during infusion. In contrast, mean wall shear rates in the arterioles and venules were not changed by SNP infusion. The results indicated that SNP and SIN-1 possessed potent antithrombotic activities, whilst SNP increased cerebral blood flow without changing wall shear rate. The findings suggest that the NO released by SNP and SIN-1 may be beneficial for the treatment and protection of cerebral infarction.

Effects of delayed treatment with nebracetam on neurotransmitters in brain regions after microsphere embolism in rats.

1. The effects of delayed treatment with nebracetam, a novel nootropic drug, on neurotransmitters of brain regions were examined in rats with microsphere embolism-induced cerebral ischaemia. 2. Cerebral ischaemia was induced by administration of 900 microspheres (48 microns) into the internal carotid artery. The rats with stroke-like symptoms were treated p.o. with 30 mg kg-1 nebracetam twice daily. The levels of acetylcholine, dopamine, noradrenaline, 5-hydroxytryptamine (5-HT) and their metabolites in the cerebral cortex, striatum and hippocampus of animals with microsphere embolism were determined by high performance liquid chromatography (h.p.l.c.) on the 3rd and 7th days after the operation. 3. Although the microsphere embolism induced significant changes in most of the neurotransmitters and some of their metabolites in the brain regions, the delayed treatment with nebracetam partially restored only the hippocampal 5-HT and the striatal dopamine metabolite contents on the 3rd day. 4. The hippocampal in vivo 5-HT synthesis, but not the striatal dopamine synthesis, was attenuated in rats with microsphere embolism on the 3rd day, but was restored by treatment with nebracetam. In vivo striatal dopamine turnover rate of the rats with microsphere embolism was inhibited on the 3rd day irrespective of treatment with nebracetam. 5. The present study provides evidence for a possible action of nebracetam on 5-HT metabolism in the ischaemic brain.

Possible therapeutic effect of naftidrofuryl oxalate on brain energy metabolism after microsphere-induced cerebral embolism.

1. The present study was designed to determine whether naftidrofuryl oxalate exerts a possible therapeutic effect on brain energy metabolism impaired by microsphere-induced cerebral embolism in vitro. 2. Injection of microspheres into the right carotid canal resulted in a decrease in tissue high-energy phosphates both in the right and left hemispheres, and an increase in tissue lactate in the right hemisphere, on the 3rd and the 5th day after the embolism. The embolism also induced a marked reduction in mitochondrial oxidative phosphorylation ability and succinate dehydrogenase activity. The results suggest that severe ischaemia was induced in the brain by the microsphere administration. 3. Treatment of microsphere-injected rats with naftidrofuryl oxalate (15 mg kg-1) for 3 or 5 days elicited a significant recovery of tissue high-energy phosphate and lactate levels. The recovery was associated with a significant restoration of mitochondrial succinate dehydrogenase activity on the both days and of mitochondrial oxidative phosphorylation rate on the 5th day. 4. The results suggest that naftidrofuryl oxalate is beneficial in the recovery of cerebral energy metabolism impaired by microsphere-induced cerebral ischaemia, presumably through a mechanism involving its direct effect on the cerebral mitochondrial enzyme activities.

Effects of delayed treatment with nafronyl oxalate on microsphere embolism-induced changes in monoamine levels of rat brain regions.

1. The present study was undertaken to examine the effects of delayed treatment with nafronyl oxalate (nafronyl), a cerebral vasodilator, on monoamine neurotransmitters of brain regions in the microsphere-embolized rat. 2. Microsphere embolism was induced by injecting 900 microspheres with a diameter of 48 microns into the right internal carotid artery of rats. Microsphere-embolized rats were treated with nafronyl, 15 mg kg-1, i.p., twice daily from the first to the 5th day. Levels of monoamines and their metabolites in the cerebral cortex, striatum, and hippocampus were measured on days 3 and 5 after the operation by a high-performance liquid chromatograph with electrochemical detection. In vivo tyrosine or tryptophan hydroxylation was estimated by measurement of the accumulation of 3, 4-dihydroxyphenylalanine or 5-hydroxy-1-tryptophan after administration of 3-hydroxybenzylhydrazine dihydrochloride, an inhibitor of aromatic L-amino acid decarboxylase. 3. Microsphere embolism induced decreases in dopamine, noradrenaline and 5-hydroxytryptamine in three brain regions of the right hemisphere on days 3 and 5. In the left hemisphere, the monoamines were reduced, but to a lesser degree than in the right hemisphere. On days 3 and 5, the decrease in the monoamines of the right hemisphere was attenuated by nafronyl treatment except for noradrenaline on day 3. The decrease in the monoamines levels in the left hemisphere was almost completely prevented by nafronyl treatment. 4. On day 3 after microsphere embolism, in vivo tyrosine and tryptophan hydroxylation was lower than the pre-embolic value in all three brain regions. Treatment of the embolized rats with nafronyl significantly attenuated the decrease in in vivo tyrosine and tryptophan hydroxylation in the ipsilateral hemisphere, but not hippocampal tryptophan hydroxylation. 5. The results suggested that treatment with nafronyl improves or attenuates changes in monoamine neurotransmitter metabolism of the brain regions impaired by microsphere embolism. The mechanisms underlying this effect may be attributed to preservation of the ability to synthesize monoamines when the brain is ischaemic or oligaemic.

Can retrograde perfusion mitigate cerebral injury after particulate embolization? A study in a chronic porcine model.

OBJECTIVE: We assessed the impact on histologic and behavioral outcome of an interval of retrograde cerebral perfusion after arterial embolization, comparing retrograde cerebral perfusion with and without inferior vena caval occlusion with continued antegrade perfusion. METHODS: Sixty Yorkshire pigs (27 to 30 kg) were randomly assigned to the following groups: antegrade cerebral perfusion control; antegrade cerebral perfusion after embolization; retrograde cerebral perfusion control; retrograde cerebral perfusion after embolization; retrograde cerebral perfusion with inferior vena cava occlusion, retrograde cerebral perfusion with inferior vena cava occlusion control, and retrograde cerebral perfusion with inferior vena cava occlusion after embolization. After cooling to 20 degrees C, a bolus of 200 mg of polystyrene microspheres 250 to 750 (microm diameter (or saline solution) was injected into the isolated aortic arch. After 5 minutes of antegrade cerebral perfusion, 25 minutes of antegrade cerebral perfusion, retrograde cerebral perfusion, or retrograde cerebral perfusion with inferior vena cava occlusion was instituted. After the operation, all animals underwent daily assessment of neurologic status until the time of death on day 7. RESULTS: Aortic arch return, cerebral vascular resistance, and oxygen extraction data during retrograde cerebral perfusion showed differences, suggesting that more effective flow occurs during retrograde cerebral perfusion with inferior vena cava occlusion, which also resulted in more pronounced fluid sequestration. Microsphere recovery from the brain revealed significantly fewer emboli after retrograde cerebral perfusion with inferior vena cava occlusion. Behavioral scores showed full recovery in all but one control animal (after retrograde cerebral perfusion with inferior vena cava occlusion) by day 7 but were considerably lower after embolization, with no significant differences between groups. The extent of histopathologic injury was not significantly different among embolized groups. Although no histopathologic lesions were present in either the antegrade cerebral perfusion control group or the retrograde cerebral perfusion control group, mild significant ischemic damage occurred after retrograde cerebral perfusion with inferior vena cava occlusion even in control animals. CONCLUSIONS: Although effective washout of particulate emboli from the brain can be achieved with retrograde cerebral perfusion with inferior vena cava occlusion, no advantage of retrograde cerebral perfusion with inferior vena cava occlusion after embolization is seen from behavioral scores, electroencephalographic recovery, or histopathologic examination; retrograde cerebral perfusion with inferior vena cava occlusion results in greater fluid sequestration and mild histopathologic injury even in control animals. Retrograde cerebral perfusion with inferior vena cava occlusion shows clear promise in the management of embolization, but further refinements must be sought to address its still worrisome potential for harm.

Differential expression of c-fos, Hsp70 and Hsp27 after photothrombotic injury in the rat brain.

In situ hybridization and immunohistochemistry were used to examine the expression of c-fos, Hsp70 and Hsp27 following photothrombotic injury in the right fronto-parietal cortex of the rat. C-fos mRNA and protein were detected in the entire cerebral cortex on the lesioned side. Hsp70 mRNA accumulation was observed only adjacent and peripheral to the site of the lesion. At 1 h after photothrombotic injury, Hsp70 expression delineates the area of necrosis at 24 h after photothrombotic injury. Hsp27 protein was observed in the ipsilateral cerebral cortex with the exception of the deep layers of the cingulate cortex. In addition, while c-Fos immunoreactivity was localized in cell nuclei, Hsp27 immunoreactivity was detected in the cytoplasm of astrocytes. These results demonstrate that unilateral cortical injury induces changes in gene expression that vary according to cell type and brain region.

Cerebral embolization in rats induced by red blood cells treated with hypertonic X-ray contrast medium.

RATIONALE AND OBJECTIVES: Hypertonic X-ray contrast media induce morphologic changes in red blood cells (RBCs) and reduce their deformability when measured in vitro. This study investigated whether RBCs treated with hypertonic contrast media could induce circulatory as well as metabolic disturbances in vivo. METHODS: Autologous blood was mixed with an equal volume of meglumine diatrizoate (306 mgI/mL); 50 microliters of this mixture was infused into the left internal carotid artery of rats 2 minutes after mixing. Five minutes after infusion, the cerebral blood flow was determined using iodo[14C]antipyrine. 31P-magnetic resonance spectroscopy (MRS), 1H-MRS and 1H-magnetic resonance imaging (MRI) of the brain were performed before and after infusion of the mixture to study changes in energy metabolites and the integrity of the blood-brain barrier (BBB), as well as the development of edema. RESULTS: The blood flow decreased by 70% to 80% in the left cerebral cortex and caudate-putamen. 31P-MRS and 1H-MRS demonstrated derangement of oxidative phosphorylation. 1H-MRI demonstrated instant destruction of the BBB and gradual progress of edema in the left hemisphere. CONCLUSIONS: These results indicate that intracarotid infusion of RBCs treated with hypertonic contrast medium can induce embolization and subsequent ischemic damage to the brain.

A topographic measurement of brain pH.

The ability of neutral red to serve as an internal pH indicator in biological systems was tested in the rat brain after parenteral adminstration of the dye. The injected dye is avidly taken up by the brain cells and is distributed mainly in intracellular organelles. The ratio of optical signals recorded from the frozen brain at 445 and 530 nm and compared with calibration curves provides pH values. Color transition of neutral red ranges from 6.0 to 8.0 pH units. Topographic application of this method is particularly useful in studying local pH changes in brains with developing ischemic foci.

Cerebral vessels express interleukin 1beta after focal cerebral ischemia.

Rapid and marked increased levels of expression of interleukin 1beta (IL-1beta) mRNA have been detected in animal models of cerebral ischemia. However, the protein production of IL-1beta and the cellular sources of IL-1beta are largely undefined after cerebral ischemia. In the present study, we have measured the cellular localization of IL-1beta protein in brain tissue from non-ischemic and ischemic mice using immunohistochemistry. Male C57B/6J (n=45) mice were subjected to middle cerebral artery (MCA) occlusion by a clot or a suture. The mice were sacrificed at time points spanning the period from 15 min to 24 h after onset of the MCA occlusion. Non-operated and sham-operated mice were used as control groups. A monoclonal anti-IL-1beta antibody was used to detect IL-1beta. In the non-operated and sham-operated mice, a few IL-1beta immunoreactive cells were detected scattered throughout both hemispheres. IL-1beta immunoreactive cells increased in the ischemic lesion as early as 15 min and peaked at 1 h to 2 h after MCA occlusion. IL-1beta immunoreactivity was detected in the cortex of the contralateral hemisphere 1 h after ischemia. By 24 h after onset of ischemia, IL-1beta immunoreactivity was mainly present adjacent to the ischemic lesion and in the non-ischemic cortex. IL-1beta immunoreactivity was found on endothelial cells and microglia. This study demonstrates an early bilateral expression of IL-1beta on endothelium after MCA occlusion in mice.

Endogenous plasminogen activator expression after embolic focal cerebral ischemia in mice.

Urokinase-type plasminogen activator (u-PA) and tissue-type plasminogen activator (t-PA) play important roles in fibrinolysis, cell migration, tissue destruction, angiogenesis and tissue remodeling. u-PA and t-PA activity in tissue are tightly regulated by plasminogen activator inhibitor-1 (PAI-1). However, little is known of the activity of endogenous plasminogen activators (PAs) and PAI-1 in ischemic brain. To evaluate whether cerebral ischemic injury induces endogenous PAs and PAI-1, we measured PA activity from brain homogenates, and examined the expression of t-PA mRNA, u-PA mRNA and PAI-1 mRNA from brain homogenates in C57BL/6J mice (n=45) weighing 29-35 g in which the middle cerebral artery (MCA) was occluded by a fibrin-rich clot. Brain homogenates were prepared for direct casein zymography from control non-ischemic mice (n=4) and mice at 2 h (n=5), 4 h (n=5), and 24 h (n=4) after MCA occlusion (MCAO). Also, u-PA and t-PA knockout mice at 4 h (n=2, each) after MCAO were used as a negative control for direct casein zymography. Frozen sections for in situ zymography were obtained from control mice (n=2) and mice at 2 h, 4 h, and 24 h (n=2, per time point) after clot occlusion. Brain homogenates were prepared for reverse transcriptase-polymerase chain reaction (RT-PCR) to examine t-PA mRNA, u-PA mRNA and PAI-1 mRNA expression from control non-ischemic mice (n=4) and mice at 2 h (n=5), 4 h (n=5), and 24 h (n=5) after MCAO. By direct casein zymography, u-PA activity increased at 4 h (P<0.05), and 24 h (P<0.05) after stroke in the ischemic hemisphere compared with the non-ischemic mice. Activity of t-PA in ischemic brain was not significantly different from the control group. As measured by in situ zymography, PA activity, most likely u-PA, was present in the ischemic hemisphere. By RT-PCR, expression of PAI-1 mRNA, but not u-PA mRNA and t-PA mRNA, increased 3-, 15- and 25-folds in the ischemic hemisphere at 2 h, 4 h and 24 h after stroke, respectively, compared with control mice. This study demonstrates that PAI-1 mRNA and u-PA activity increase in mouse brain after stroke.

Microsphere embolism-induced changes in noradrenaline uptake of the cerebral cortex in rats.

The present study was undertaken to elucidate pathophysiological changes in noradrenaline (NA) transporter and Na+/K+-ATPase, key regulators of cation gradient across the plasma membrane, in nerve terminals of the cerebral cortex after microsphere-induced cerebral embolism in rats. The Vmax value of NA uptake, when analyzed by the Eadie-Hofstee plot, tended to decrease on the 1st day and decreased on the 3rd and 7th days after the embolism without any change in the Km value. The NA content in cerebrocortical synaptosomes did not alter on the 1st day, but decreased on the 3rd and 7th days after the embolism. Ouabain (1 mM) inhibited NA uptake on the 1st day, but did not alter the uptake on the 3rd and 7th days after the embolism. The activity of Na+/K+-ATPase of cerebrocortical synaptosomes increased on the 1st day and gradually decreased up to the 7th day after the embolim. These results suggest that NA uptake in nerve terminals of the cerebral cortex decreased after microsphere embolism, which may be due to a reduction in function of NA transporters. The changes in Na+/K+-ATPase following microsphere embolism may represent a compensatory action to maintain ion homeostasis in nerve terminals at an early stage of ischemic injury.